I got two G20 mags when I bought the 6" barrel. And after I shot the 40 I found that I had to do the "KKM" conversion on my extractor. I shot some 10mm after that and everything was ok, but I haven't had a chance to run any more 40 through it. Also, it's not as positive an ejection as the 45 but the 40 does eject when I cycle some by hand.

But, to get back to the OP's point, I did pick up a value box of Rem 40 S&W JHP that I intend to run through my factory G20 6" barrel. I want to see if the mod to the G21 extractor will fix the ejection problem with the 40 caliber rounds. And I need to see if maybe their might be a problem with the Underwood 135gr primers being a little too hard.

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G29SF, G38 w/lasermax, The 21 Club #7663, The 10 Ring #7663, The Bull Dawgs Club #7663, US Army Veteran